Maybe u should try to look at this picture at the same time listen to Twitch's remix of The Changeling. It's a very cool song. But it's a remix, and the original is kinda slow. But they are both awesome! Check it out! Link: www.youtube.com/watch?v=NXnwQ9…
You know, Changelings are what happens when you feed Breezies after midnight. ;D
There's a story in this, which I'm surprised no one picked up on yet as far as I can find in fanfiction: Discord created the changelings from a pack of lost Breezies. Or maybe Sombra did it. Or NMM. Or Tirek. Or Grogar. Or Sauron. Or any of a long list of supervillains who make twisted minions.
I think I've seen more than one story where Discord made the changelings out of the Flutter Ponies. I can remember at least one for sure. So that sort of thing has kind of -ish been done before. I haven't seen a "Discord created the changelings" story recently enough for them to be from the breezies, though. And the stories where he did that painted him darker than good old redeemed-ish Discord.
Still could be Sombra or Tirek, though, as you said.
I have an idea for the Changelings from Flutterponies, using Discord, that hasn't been done.
There's really no need to make him darker, just a tad more conniving and duplicitous. It would mark Discord's entry into Equestria, they would be the doorway he'd need to enter their world physically. In my mind, he's a spirit that needs to be invited in, much like disharmony must be fostered in one's heart and mind for it to exist.
And so, after Flutter Valley is left frozen by the windigoes and the ponies simply abandon them to their fate in their exodus to the new Equestria, the Flutters cry out in rage and betrayal, their Queen vowing revenge on the ponies... and Discord hears her plea and grants her wish, letting him slip in and turning the Flutterponies into Changelings.
Aghast at their horrible new appearance, Discord merely comments he made them look like what their Queen was feeling: hard, cold, broken, incomplete.
They come to accept it when they realize how powerful they are in their new forms, and how their shapeshifting powers will let them have the revenge they crave.
And this, then, sets the stage for everything in canon, including Chrysalis' ill-conceived invasion plan (which, being driven by such a long-held lust for revenge passed down the royal line, led to delusions of grandeur and irrational ideations.)